LISA Frequency Reference System LISALSR-FRS-REQ-0067, Revision A-

Effective Date: April 22, 2026 ii

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LISA Frequency Reference System

Review/Signature/Approval Page

Prepared by:

Sydney Roberts

Reviewers/Approvers:

John Canham

Judy Brannen

David Guzman Garcia

Victor Sigmund

Zachary (Zach) Denny

Ali Feizi

Thomas Emmett

Sharon Peabody

Materials

Mollie Grossman

Peng Chen

Matthew (Matt) Joplin

Paula Pruessner

Bradley Weidema

Rachel Safran

Denis Pinha

Approved by:

Zachary (Zach) Denny

*** Electronic signatures are available on-line at: https://ipdtdms.gsfc.nasa.gov

LISA Frequency Reference System LISALSR-FRS-REQ-0067, Revision A-iii

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Preface

This document is under control by the LISA project configuration control board (CCB).

Changes to this document require prior approval of the LISA CCB chairperson or designee.

Proposed changes shall be submitted in the LISA Technical Data Management System (TDMS) via a configuration change request (CCR) along with supportive material justifying the proposed change. Changes to this document will be made by complete revision.

All of the requirements in this document assume the use of the word "shall" unless otherwise stated.

Questions or comments concerning this document should be addressed to:

LISA Configuration Management Office (CMO)

Mail Stop: 462

Goddard Space Flight Center

Greenbelt, Maryland 20771

LISA Frequency Reference System LISALSR-FRS-REQ-0067, Revision A iv

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Change History Log

Revision Effective Date Description of Changes

(Reference the CCR & CCB/ERB Approval Date)

Revision - 01/05/2026 Baseline Release following the Approval of LISALSR-

SCoRe-0154

Revision A 04/22/2026 Revision A Released following the Approval of

LISALSR-SCoRe-0205 v

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Table of TBDs/TBRs/TBSs

Item

No.

Location TBX

Summary

TBX

Assignee

TBX

Due

Date

1 LISALSR-THRM-ICD-0032 TBR 2.2.0

1.1.1 3.2.3 FRS-E Dimensions

The FRS-E shall be compliant with the volume allocations per the MICD 2351681 TBD.

Note: FRS-E dimensions will not exceed 0.30m (X) x 0.15m (Y) x 0.27m(Z).

3.2.3

1.1.2 3.2.4 FRS-O Dimensions

The FRS-O shall be compliant with the volume allocation per the MICD 2360570 TBD.

Note: FRS-O dimensions will not exceed 0.55m (X) x 0.22m (Y) x 0.25m (Z).

3.2.4

4 The vent duct flange, defined in MICD 2360570

TBD, attached to FRS-O shall be confined to allocated FRS-O dimensions per the FRS-O MICD

2360570 TBD.

3.2.4

1.1.3 3.3.1 OICD Compliance

The FRS shall comply to the FRS Optical Interface

Control Document (OICD) TBD.

This includes information on:

- input laser wavelength

- fiber optic inputs

- polarization extinction ratio (PER)

- laser input power

3.3.1

1.1.4 3.3.2 Laser Frequency Modulation

The FRS shall, when set to the Reference Locked substate, implement a sinusoidally varying offset creating a frequency modulation of amplitude between 100 Hz TBR and 2 kHz, with step size of

10 Hz at a frequency between 1 mHz and 1 Hz.

3.3.2

1.1.5 3.3.3 Laser Frequency Stability -

Reference Mode

The FRS shall meet the following frequency stability requirement for a laser operating in the

Reference mode:

for 0.1 mHz ≤ f < 1 kHz, sqrt(G_v) = 30

Hz/sqrt(Hz) * sqrt(1 + (2mHz/f)^4)

3.3.3 vi

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Item

No.

Location TBX

Summary

TBX

Assignee

TBX

Due

Date for 1 kHz ≤ f < 5 MHz, sqrt(G_v) = 3.75

Hz/sqrt(Hz) * sqrt(1 + (8kHz/f)^2) TBD for 5 MHz ≤ f < 60 MHz, sqrt(G_v) = 10

Hz/sqrt(Hz)

1.1.6 3.3.18 Loss of Laser Frequency Lock

Loss of frequency lock due to a transient event caused by radiation lasting longer than TBD ms shall have a probability of less than 6 x 10^-5 per constellation per day, a less than 10% chance of happening for the mission TBC.

3.3.18

1.1.6.1 3.4.4.2 Configurable Telemetry Sampling

Rate

The capability shall be provided to sample a given telemetry parameter at a configurable sampling rate down to a minimum sampling interval 125 milliseconds. TBR

3.4.4.2

1.1.6.2 3.4.4.3 Telecommand Reception and

Execution Rate

The FRS shall receive and execute telecommands at a rate of TBD commands per second for real-time commands and TBD commands per second for queued commands.

3.4.4.3

1.1.6.3 3.4.4.4 Monitor Telemetry Set

The FRS shall provide TBD monitor telemetries to enable FRS operation, performance optimization, and problem diagnosis and resolution. The FRS telemetry shall include as a minimum: unit internal power monitor diodes and unit internal temperature sensors.

3.4.4.4

1.1.6.4 3.4.6.6 Power Supply Protection

Monitoring

All current limiting devices and automatic switch off circuits shall be monitored by telemetry. TBR

3.4.6.6

1.1.6.5 3.4.7.5 FRS Ground Lug/Bolt Location

The FRS-E and FRS-O shall provide the negotiated ground lug/ground bolt location as shown in the

MICD. TBC

3.4.7.5 vii

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Item

No.

Location TBX

Summary

TBX

Assignee

TBX

Due

Date

1.1.6.6 3.4.16.16 Operation Through LFPDC

Synchronization Loss/Recovery

The FRS (LFPDC, FCC) shall continue to operate during loss and subsequent recovery of the LFPDC synchronization. TBR

3.4.16.16

1.1.6.7 3.4.16.17 LFPDC Synchronization Signal

Enable/Disable Command

The FCC shall have a command which enables/disables synchronization signal to the

LFPDC. TBR

3.4.16.17

1.1.7 3.5.1 TICD Compliance

The FRS shall adhere to the Thermal ICD TBD.

3.5.1

1.1.8 3.5.8 FRS Maximum Transient Heat

Flux

The maximum transient heat flux on the FRS baseplate shall not be greater than 1.5 times the average heat flux. TBR

3.5.8

1.1.9 3.6.1 FRS-O MICD

The FRS-O shall comply with NASA GSFC MICD

2360570 TBD.

3.6.1

1.1.10 3.6.2 FRS-E MICD

The FRS-E shall comply with NASA GSFC MICD

2351681 TBD.

3.6.2

1.1.11 3.6.3 MICD Definition

The FRS MICDs shall contain, as a minimum, the following set of interface information:

• Drawing Identification Code and date of issue;

• Dimensions and associated tolerances (at ambient temperatures), including feet, external connectors and their dedicated clearance;

• Provide details of all co-ordinate systems utilized and their relationship to each other, together with the principal unit interfaces;

• Identification of the Unit Physical Reference

Frame (URF) and Reference Hole (RH);

• Identification of the Thermal Reference Point

(TRP);

3.6.3 viii

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Item

No.

Location TBX

Summary

TBX

Assignee

TBX

Due

Date

• Mounting hole pattern dimensions and hole patterns;

• Dimensions of mounting feet and contact area

(base-plate and mounting feet);

• Spot-faced area for seating of the mounting screw washers (TBD);

• Mass and associated tolerances (precise if estimated, calculated or weighted);

• Location, naming, type and function of all connectors (per EICD);

• Location and dimensions of venting holes;

• Connector key shape orientation, the identification of connector contact “1”, showing connector in front view and the connector center line (per EICD);

• Information about connector fixation (per EICD);

• Identification and details of grounding studs and grounding straps;

• Identification of non-flight items (i.e red tag items);

• Location of handling points (e.g. threaded bushes);

• Location of unit and connector identification labels;

• Identification of the envelope of each red- and green-tag item;

• Details of instrument provided mounting hardware, thermal/electrical isolation

-TRP locations provisions like: thermal strap(s) material, dimensions, I/F, mounting area location, dimension, flatness, finishes, roughness;

number/type of thermal strap mounting bolts and their torque, presence of filler;

• Location of operational and non-operational temperature sensors (for test and flight purpose)

(TBD);

• Centre of Gravity coordinates, calculated and specified wrt URF;

• Moments of Inertia coordinates, calculated and specified wrt URF;

• Surface coating (IR Emittance and Solar absorptance if external location) (TBD);

• Specific heat (J kg–1 K–1) (calculated or measured) (per TICD);

ix

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Item

No.

Location TBX

Summary

TBX

Assignee

TBX

Due

Date

• Identification and orientation of any strong permanent magnetic field component when present.

1.1.12 3.6.10 FRS-O Mechanical Interface

The FRS-O mechanical interface with the

Spacecraft shall meet the FRS-O MICD 2360570

TBD.

3.6.10

1.1.13 3.6.15 Vent Duct Rate

The spacecraft vent duct shall guarantee a vent rate of 1 L/s (TBC) to the FRS-O.

3.6.15

1.1.14 3.7.11 Generated Frequency

Restrictions

The FRS shall not utilize nor generate 98304 ± 1 kHz and 14706 ± 100 Hz TBR frequencies.

Note: Energy generated via harmonics of lower frequency or subharmonics of higher frequency are also limited by this specification.

3.7.11

1.1.14.1 3.7.16.2 FRS-E Radiative Thermal

Environment

FRS-E analysis shall assume a black body cavity temperature range of 10°C to 30°C TBR.

Note: FRS-E analysis shall assume a black body cavity temperature of:

+10°C for cold biased analyses TBR

+30°C for hot biased analyses TBR

3.7.16.2

1.1.14.2 3.7.17.8 FRS-E Permanent Magnetic

Field Contribution

Current loops in the FRS-E structure and Printed

Wiring Assemblies shall contribute less than 25

TBC mAm^2 of the FRS-E permanent magnetic field contribution.

3.7.17.8

1.1.14.3 3.7.17.9 FRS-O Permanent Magnetic

Field Contribution

Current loops in the FRS-O structure and Printed

Wiring Assemblies shall contribute less than 25

TBC mAm^2 of the FRS-O permanent magnetic field contribution.

3.7.17.9 x

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Item

No.

Location TBX

Summary

TBX

Assignee

TBX

Due

Date

1.1.14.4 3.7.17.10 FRS-E Permanent Remanent

Field Contribution

The permanent remanent field of the FRS-E in an unpowered state shall be less than 25 TBC mAm^2.

3.7.17.10

1.1.14.5 3.7.17.11 FRS-O Permanent Remanent

Field Contribution

The permanent remanent field of the FRS-O in an unpowered state shall be less than 25 TBC mAm^2.

3.7.17.11

1.1.15 3.9.3 Cleanliness Bakeout

The FRS shall go through a time/temperature bakeout of TBD°C for TBD hours (TBR) under vacuum.

3.9.3 xi

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Table of Contents

1 Introduction

1.1 General Information

2 Related Documents

2.1 Applicable Documents

2.2 Reference Documents

3 Requirements

3.1 Lifetime Requirements

3.2 Functional Requirements

3.3 Performance Requirements

3.4 Electrical Requirements

3.5 Thermal Requirements

3.6 Mechanical Requirements

3.7 Environmental Requirements

3.8 Radiation Requirements

3.9 Contamination Requirements

3.10 Material Requirements

Appendix A.Traceability Matrix

Appendix B. Abbreviations & Acronyms xii

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List of Figures

Figure 3-1: Vacuum Fitting Orientation Figure 3-2: FRS-O Tube Angle Figure 3-3: FRS-E shock Figure 3-4: FRS random vibration

List of Tables

Table 2-1: Applicable Documents Table 2-2: Reference Documents Table 3-1: FRS-O shock Table 3-2: FRS-E shock Table 3-3: FRS random vibration levels – proto-flight levels (all axes) Table 3-4: FRS sine vibration level

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1 INTRODUCTION

1.1 General Information

The National Aeronautics and Space Administration (NASA) and European Space Agency

(ESA) collaborative Laser Interferometer Space Antenna (LISA) mission uses three bi-directional laser links with cross polarized beams to link its three spacecraft to measure differential changes in distances between on-board test masses on the level of just a few picometers. These picometer fluctuations in test mass distances could signify the presence of a gravity wave, as the distances between test masses shall fluctuate with the expanding and contracting of space time caused by the passing of gravity waves. Due to the small scale of these fluctuations and therefore the incredible accuracy required to measure them, mission-wide suppression of measurement noise is paramount.

The LISA Frequency Reference System (FRS), which consists of the FRS Optical Cavity (FRS-

O) and FRS Electronics (FRS-E), will be used in concert with the Main Oscillator Power

Amplifier (MOPA) laser to achieve low frequency noise requirement. The FRS utilizes the

Pound-Drever-Hall technique (PDH) for frequency stabilization. A small fraction of the Main

Oscillator (MO) light from the Laser Optical Module (LOM) is injected into the FRS-O dedicated Phase Modulator (PM), which provides the side band necessary for the PDH scheme to stabilize the laser frequency to match the resonant frequency of the optical cavity. The design of the FRS-O is such that its interior consists of two parallel mirrors facing inward, spaced such that the round-trip distance between them equals an integer multiple of the desired ‘reference’ wavelength, 1064.5nm for the Laser System (LS). The light injected into the FRS-O which is close to the desired frequency will constructively interfere with itself each round trip, building up in the cavity, while light with a frequency sufficiently far from the reference frequency will destructively interfere and be reflected back. Photodiodes detect this reflected light, which has now interfered with the reference frequency light and as such contains information related to the interference. The signal from the photodiode can then be analyzed to generate an error signal that defines how far the laser frequency is from the cavity reference frequency, allowing the laser system to determine how much adjustment is needed in the MO to output the desired frequency.

This process is controlled by the FRS-E and repeated continuously to form a feedback loop that will ensure high precision laser stability.

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2 RELATED DOCUMENTS

2.1 Applicable Documents

The following documents are referenced within this document and are directly applicable or contain policies or other directives that are binding for the contents of this document. In the event of conflict between an Applicable Document and the content of this document, the LISA

Project Configuration Change Board has the final authority for conflict resolution.

Table 2-1: Applicable Documents Document Number Title

LISALSR-SYS-REQ-0040 LISA Laser Systems Requirements Document GSFC-STD-7000A General Environmental Verification Standard (GEVS) LISA-SMA-REQ-0010 LISA Mission Assurance Requirements

2.2 Reference Documents

The following documents are referenced herein and amplify or clarify the information presented in this document. These documents are not binding on the content of this document.

Table 2-2: Reference Documents Document Number Title GSFC EEE-INST-002 Instruction for EEE Parts Selection, Screening, Qualification, and Derating

LISA-ELEC-ICD-

Laser System Tuning Digital Interface

LISALSR-FRS-ICD-

NASA-controlled FRS-E ICD

NASA-STD-5020 Requirements for Threaded Fastening Systems in Space Flight Hardware 540-PG-8072.1.2 Mechanical Fastener Torque Guidelines

NASA-STD-5020A

w/CHANGE Requirements for Threaded Fastening Systems in Space Flight Hardware

NASA-STD-5019A

w/CHANGE Fracture Control Requirements for Spacecraft Hardware

2360570 NASA GSFC MICD FRS-O

2351686 NASA GSFC MICD FRS-E

LISA-ELEC-ICD-

NASA LISA Laser System EICD

LISA-ELEC-ICD-

LISA Laser System Telemetry and Telecommands

LISA-ELEC-PLAN-

NASA Electrical Systems Specification

LISA-ELEC-PLAN-

LISA Laser System Electromagnetic Compatibility (EMC) Control Plan

LISA-SMA-PLAN-

LISA Materials and Processes Selection, Control, and Implementation Plan

LISA-ELEC-PLAN-

LISA Magnetics Plan

LISA-SYS-DESC-

LISA Laser System – Grounding and Bonding Diagram

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NASA-HDBK-4002B NASA Handbook

ESA-L3-EST-MIS-

SP-001

ESA Mission Specs

LISA-SMA-PLAN-

Laser System EEE Parts Control Plan (PCP)

LISALSR-THRM-

ICD-0032 TBR

NASA LISA Laser FRS-O Thermal ICD

LISA-LASER-REQ-

ESA:LISA Laser System and Interface Requirements Document (IRD 2)

LISA-SYS-REQ-

Radiation Hardness Assurance Requirement Document (RHARD)

LISA-SYS-REQ-

LISA Radiation Engineering Input to Environmental Requirements (RADER)

ASTM-E595

Standard Test Method for Total Mass Loss and Collected Volatile Condensable

Materials from Outgassing in a Vacuum Environment

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3 REQUIREMENTS

3.1 Lifetime Requirements

3.1.1 FRS Composition

FRS-295 The Frequency Reference System (FRS) shall be composed of an FRS-E (electronics unit) and an FRS-O (optics unit).

Note: FRS will refer to both the FRS-E and FRS-O. Specific requirements to the electronics or optics box will be called out as such.

Note: The FRS will interface with the Laser Head (LH), which is composed of the Laser

Electrical Module (LEM) and Laser Optical Module (LOM), and be a subsystem of the Laser

System (LS).

3.1.2 Lifetime - Ground

FRS-2 The FRS shall meet the requirements of its specification on-ground lifetime of up to 8 years including up to 2 years in storage after delivery to ESA.

Rationale: To meet lifetime requirements.

3.1.3 Lifetime - Post Launch

FRS-1 The FRS shall survive, perform, and functionally operate during a total of 6.5 (Earth) years post launch.

Note: The Extended Science Phase (ESP) will be 5.5 years beyond nominal mission lifetime.

Rationale: Baseline mission phases are as follows:

Launch and Early Orbit Phase (LEOP): 3 days

Transfer Phase (TP) including Near Earth Commissioning Phase (NECP): 18 months

System Commissioning and Calibration Phase (SCCP): 3 months

Nominal Science Phase (NSP): 4.5 years

Decommissioning Phase (DCP): 7 days

3.1.4 Reliability

FRS-7 The reliability of the FRS shall be 0.84 at 4.5 years.

Rationale: To meet reliability requirements. Assumed at 20C and nominal functioning.

3.1.5 FRS-E Redundancy

FRS-154 The FRS-E shall interface to and be able to drive all four LEMs in the LS on a

Spacecraft (SC).

Note: The FRS-E will only drive one LEM at a time.

Rationale: To satisfy laser switching.

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3.1.6 FRS-O Redundancy

FRS-153 The FRS-O shall interface to and accept all four LOMs in the LS on a SC.

Rationale: To satisfy laser switching.

3.1.7 Redundancy

FRS-80 The FRS shall communicate, tune, and stabilize one LH at a time from among the 4

LHs in the LS on a SC.

3.1.8 Failure Propagation - LH

FRS-158 No single failure in the FRS shall propagate to a failure in any LH.

3.1.9 Failure Propagation - LISA Platform

FRS-159 No single failure in the FRS shall propagate to the LISA platform.

3.1.10 Failure Propagation - Redundant Side

FRS-279 No single failure within the FRS shall result in the loss of more than one power input

(i.e., no failure propagation to the redundant side).

3.2 Functional Requirements

3.2.1 FRS-E Mass Allocation

FRS-27 The FRS-E consisting of the chassis, power card (LFPDC) and FRS-E control card

(FCC) shall not exceed 4.0 kg.

Note: This does not include associated harnessing, nor the FRS-E internal harnesses between the

LFPDC and FCC cards.

Rationale: The mass is an interface requirement that must be satisfied.

3.2.2 FRS-O Mass Allocation

FRS-28 The FRS-O mass shall not exceed 9.8 kg.

Rationale: The mass is an interface requirement that must be satisfied.

3.2.3 FRS-E Dimensions

FRS-53 The FRS-E shall be compliant with the volume allocations per the MICD 2351681

TBD.

Note: FRS-E dimensions will not exceed 0.30m (X) x 0.15m (Y) x 0.27m(Z).

3.2.4 FRS-O Dimensions

FRS-52 The FRS-O shall be compliant with the volume allocation per the MICD 2360570

TBD.

Note: FRS-O dimensions will not exceed 0.55m (X) x 0.22m (Y) x 0.25m (Z).

FRS-269 The vent duct flange, defined in MICD 2360570 TBD, attached to FRS-O shall be confined to allocated FRS-O dimensions per the FRS-O MICD 2360570 TBD.

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3.2.5 Power Allocation

FRS-30 The FRS power when averaged over any 60 second interval shall not exceed 21W.

Rationale: The power is an interface requirements that must be satisfied.

3.2.6 Mode Request Receipt and Action

FRS-296 The FRS shall receive and act on mode requests from the LH.

3.3 Performance Requirements

3.3.1 OICD Compliance

FRS-297 The FRS shall comply to the FRS Optical Interface Control Document (OICD) TBD.

This includes information on:

- input laser wavelength

- fiber optic inputs

- polarization extinction ratio (PER)

- laser input power

3.3.2 Laser Frequency Modulation

FRS-9 The FRS shall, when set to the Reference Locked substate, implement a sinusoidally varying offset creating a frequency modulation of amplitude between 100 Hz TBR and 2 kHz, with step size of 10 Hz at a frequency between 1 mHz and 1 Hz.

Rationale: Laser frequency modulation is required for TDI calibration during commissioning.

3.3.3 Laser Frequency Stability - Reference Mode

FRS-10 The FRS shall meet the following frequency stability requirement for a laser operating in the Reference mode:

for 0.1 mHz ≤ f < 1 kHz, sqrt(G_v) = 30 Hz/sqrt(Hz) * sqrt(1 + (2mHz/f)^4) for 1 kHz ≤ f < 5 MHz, sqrt(G_v) = 3.75 Hz/sqrt(Hz) * sqrt(1 + (8kHz/f)^2) TBD for 5 MHz ≤ f < 60 MHz, sqrt(G_v) = 10 Hz/sqrt(Hz)

Rationale: To match the frequency noise in linear PSD specifications.

3.3.4 Laser Locking

FRS-11 The FRS-O shall apply Pound-Drever-Hall laser locking to a reference cavity.

Rationale: To meet the laser frequency stability requirement using an established laser locking approach.

3.3.5 Cavity Finesse

FRS-12 The FRS-O reference cavity Finesse shall be 12,000-15,000.

Rationale: To meet the laser frequency stability requirement using an established laser locking approach.

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3.3.6 Spurious Etalon Mitigations

FRS-298 Once determined, the FRS-O cavity Finesse shall not change over the operating temperature range.

3.3.7 Free Spectral Range

FRS-299 The Free Spectral Range (FSR) shall be 1.93GHz ± 0.01GHz.

3.3.8 Cavity Scanning

FRS-15 The FRS shall have autonomous scanning using both feedback loops over at least 1 cavity FSR.

Rationale: Functionality is needed without manual adjustments.

3.3.9 Cavity Locking

FRS-16 The FRS shall have a re-lock algorithm using both feedback loops over at least 1 cavity FSR.

Rationale: Functionality is needed without manual adjustments.

3.3.9.1 Resonance Scan and Storage

FRS-300 The FRS shall have the capability to perform a resonance scan while storing responses above a programmable threshold which can later be transferred to the LH for downlink.

3.3.9.2 Autonomous Acquire After Loss of Lock

FRS-301 The FRS shall have a capability to autonomously acquire after a loss of frequency lock with a programmable number of retries.

3.3.9.3 Loss of Lock Counter

FRS-302 The FRS shall have a resettable counter which counts the number of loss of lock.

3.3.9.4 Auto-acquisition Counter

FRS-303 The FRS shall have a resettable counter which counts the number of auto-acquisitions.

3.3.10 Auto-locking Acquisition Retry Configuration

FRS-147 The FRS-E shall have the capability to command the desired number of retries in the auto-locking acquisition.

Rationale: Including retries in auto-locking increases the likelihood of successful lock during flight.

3.3.11 Re-locking Time After Frequency Disturbance

FRS-304 If there is a loss of lock, the FRS-E shall automatically relock within 15 minutes.

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3.3.12 Auto-locking Failure Mode Indication

FRS-148 The FRS-E shall indicate the failure mode(s) present upon each initial auto-locking acquisition retry.

Note: The FRS-E failure mode(s) indication(s) will state at which stage of auto-locking (slow-only, slow+fast, or final fast-only scan) the failure occurred.

Rationale: The modes of failure should be interpretable and explicitly understood for debugging purposes.

3.3.13 Lock Acquired Status Reporting

FRS-151 The FRS-E shall only send "normal" or "main lock acquired" statuses when there is a successful lock to the FRS-O.

Note: The FRS-E will monitor the Tx PD voltage locked status to determine successful locking to the FRS-O.

Rationale: The FRS-E must have a clear status of whether the system is locked or un-locked.

The Tx PD threshold value can be compared against the real-time Tx PD voltage to determine whether lock was achieved.

3.3.14 Output to Phase Modulator

FRS-17 The FRS-E shall output a commandable, tunable 2-3 MHz radio frequency (RF) sinusoidal wave over SMA for the FRS-O phase modulator.

Rationale: The phase modulation signal has to be provided by the FRS-E unit for the phase modulator. 2-3MHz is determined from the photodetector bandwidth GFO used.

3.3.15 Unity Gain Frequency

FRS-18 The FRS shall have a Servo loop's unity gain frequency greater than 10kHz.

Rationale: To suppress the laser frequency noise RMS. Need high enough bandwidth to make the reference laser quiet.

3.3.16 Servo Gain Stability in Reference Mode

FRS-152 Servo Gain shall not require adjustments while FRS is in Reference Mode.

Rationale: Minimize spurious etalons during assembly. We should not be touching any frequency locking parameter to maintain frequency lock.

3.3.17 Signal Modulation/Demodulation

FRS-19 The FRS shall use RF signal modulation/demodulation, adjustable frequency 2-3

MHz.

Rationale: To produce the required frequency from the incoming clock reference signal.

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3.3.18 Loss of Laser Frequency Lock

FRS-23 Loss of frequency lock due to a transient event caused by radiation lasting longer than

TBD ms shall have a probability of less than 6 x 10^-5 per constellation per day, a less than 10% chance of happening for the mission TBC.

Rationale: Loss of frequency lock will disrupt science operations.

3.3.19 LH to FRS-O Fiber Length

FRS-24 The maximum length of the Laser Head (LH) - FRS-O optical fibers shall be 7.5m.

Rationale: Harness length is a critical aspect of performance.

3.3.20 FRS-O - FRS-E Harness Length

FRS-25 The maximum length of the FRS-O to FRS-E harnesses shall be 6m.

Rationale: Harness length is a critical aspect of performance.

3.3.21 FRS-E to LEM Harness Length

FRS-26 The maximum length of the FRS-E to Laser Electronics Module (LEM) harnesses shall be 8.2m.

Rationale: Harness length is a critical aspect of performance.

3.3.22 Frequency Stabilization Servo Minimum Phase Margin

FRS-305 The FRS-E frequency stabilization servo shall have a minimum 45-degree phase margin at the unity gain frequency.

3.3.23 Frequency Stabilization Servo Minimum Gain Margin

FRS-306 The FRS-E frequency stabilization servo shall have a minimum gain margin of at least 9 dB.

3.4 Electrical Requirements

3.4.1 FRS-E ICD

FRS-72 The FRS shall comply with the FRS-E ICD LISALSR-FRS-ICD-0031.

3.4.2 FPGA Firmware Version Readout

FRS-307 FRS-E FPGA shall be able to read its version out over the electrical interface.

3.4.3 Parts Qualification

FRS-77 The FRS shall adhere to the LISA LS EEE Parts Control Plan (PCP): LISA-SMA-

PLAN-0040.

Note: The FRS will meet Level 2 qualification as identified in GSFC EEE-INST-002, Instruction for EEE Parts Selection, Screening, Qualification, and Derating.

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3.4.4 Telemetry and Telecommands

3.4.4.1 Telemetry and Telecommands Compliance

FRS-70 The FRS shall adhere to the requirements in the LISA LS Telemetry and

Telecommands document LISALSR-FRS-ICD-0031.

Note: This is the government controlled version of the FRS EICD.

3.4.4.2 Configurable Telemetry Sampling Rate

FRS-255 The capability shall be provided to sample a given telemetry parameter at a configurable sampling rate down to a minimum sampling interval 125 milliseconds.

TBR

3.4.4.3 Telecommand Reception and Execution Rate

FRS-278 The FRS shall receive and execute telecommands at a rate of TBD commands per second for real-time commands and TBD commands per second for queued commands.

3.4.4.4 Monitor Telemetry Set

FRS-160 The FRS shall provide TBD monitor telemetries to enable FRS operation, performance optimization, and problem diagnosis and resolution. The FRS telemetry shall include as a minimum: unit internal power monitor diodes and unit internal temperature sensors.

3.4.5 Power Interface

3.4.5.1 Bus Voltage Rate of Rise

FRS-164 The FRS-E shall operate nominally and meet all performance requirements with a main bus voltage rate of rise between 60 V/msec and 600 V/msec.

3.4.5.2 Main Bus Voltage Rise Verification

FRS-165 The FRS-E shall verify the survival of any main bus voltage rate of rise by analysis.

Note: Undervoltage lockouts are implemented so as to meet this requirement.

3.4.5.3 LCL Class 2 Compliance

FRS-166 The FRS-E shall comply with the current limitation performance of the LCL class 2 as detailed below:

Min trip 10 msec

Max trip 20 msec

Max capacitance 272 uF

3.4.5.4 Circuit Limiting Circuitry Restriction

FRS-167 The FRS-E shall not implement any current limiting circuitry within their primary power interface. This restriction explicitly includes inrush limiters.

Note: The LCL provides OVP and allows for inrush.

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3.4.5.5 Maximum Current Rate of Change

FRS-168 Outside of initial inrush current at switch-on, the FRS shall have a current rate of change not to exceed 1×10⁵ A/s.

3.4.6 Power Supply Design

3.4.6.1 Power Regulation Phase and Gain Margin

FRS-169 Converters and regulators shall maintain a minimum phase margin of 50° and a gain margin of 6 dB under worst-case end-of-life conditions with representative loading.

Compliance shall be verified by stability analysis and test.

3.4.6.2 Maximum Input Serial Inductance

FRS-170 The FRS shall have an input serial inductance of less than 300 µH.

3.4.6.3 Zero-volt Reference Unit Case Isolation Resistance

FRS-171 For isolated converters and regulators, the primary power return (0 V reference) shall be isolated from the unit case by at least 10 kΩ per converter.

3.4.6.4 Zero-volt Reference Unit Case Isolation Capacitance

FRS-172 For isolated converters and regulators, the capacitance between the primary power return (0 V reference) and the unit case shall be less than 150 nF per converter.

3.4.6.5 Failure-induced Conducted Emission Limit

FRS-173 No single failure shall cause conducted emissions to exceed the specified limit by more than 6 dB. Complete inductor failures are considered not credible for this requirement.

Notes: NASA utilizes multiple filtering caps to ensure the failure of a single filtering cap does not increase EMI past 6dB. This requirement is related to the input filter + DC/DC converter.

The input filter capacitors should be sized to avoid CE on the main bus even in case of 1 failure.

NASA does not consider the total failure/short of an input inductor to be credible.

3.4.6.6 Power Supply Protection Monitoring

FRS-175 All current limiting devices and automatic switch off circuits shall be monitored by telemetry. TBR

3.4.7 Bonding and Grounding

3.4.7.1 Grounding Diagram

FRS-190 The FRS-E, FRS-O shall comply with the FRS grounding diagram: LISALSR-FRS-

DESC-0013.

3.4.7.2 FRS Grounding

FRS-261 The FRS-E and FRS-O shall implement two ground strap attachment locations as defined in the MICD.

- Support a bonding strap with a contact area > 1 cm²

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- Be placed as close as practical to the mounting base (e.g. 20 mm)

- Be installed so that neither the stud nor the bonding strap interferes with movable components(e.g., harnesses).

3.4.7.3 Charging

FRS-91 All FRS conductive elements with projected area of 3 square cm or greater shall be

ESD grounded with a resistance less than 1M Ohm.

3.4.7.4 FRS-O Vent Duct Grounding

FRS-99 The FRS-O vent duct shall be grounded to the FRS-O structure.

3.4.7.5 FRS Ground Lug/Bolt Location

FRS-101 The FRS-E and FRS-O shall provide the negotiated ground lug/ground bolt location as shown in the MICD. TBC

3.4.7.6 FRS-E Ground

FRS-102 The FRS-E signal ground is tied to the FRS-E chassis.

3.4.7.7 PCB Grounding Specification

FRS-176 The FRS-E PCB shall ground secondary power return plane to the payload level unit chassis at least at the four corners of the PCB with DC connections or AC capacitance coupling as required by the DC magnetics analysis.

3.4.7.8 Harness Routing Through Dedicated Wires

FRS-180 The FRS shall route all electrical power (primary/secondary) and signal returns through dedicated wires.

Note: No element is allowed to use the structure as an intentional return path.

3.4.7.9 Grounding Stud-Connector Resistance

FRS-104 The DC resistance between the equipment grounding/bonding stud and each connector housing shall be less than 10 mOhm.

3.4.7.10 Grounding Unused Pins

FRS-118 All unused pins of unit connectors shall be either grounded to chassis or connected to chassis via a bleeder resistor less than 1MOhm.

3.4.7.11 Secondary Power Supply Specification

FRS-179 The FRS-E and FRS-O shall provide a DC reference for all secondary power supplies inside the unit and have their return grounded to a low impedance grounding reference (chassis).

3.4.7.12 Secondary FRS-E Power Reference

FRS-188 The FRS-E shall reference secondary power provided to the FRS-O to spacecraft structure.

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3.4.7.13 Thermistor Isolation

FRS-189 Thermistors shall be galvanically isolated from the spacecraft structure with a resistance > 10MOhm and capacitance < 50nF.

3.4.7.14 Bond Environmental Tolerance

FRS-182 Each bond shall withstand vibration, expansion, contraction or relative movement of parts without breaking or loosening the bond or causing a change in contact resistance.

3.4.7.15 Conductive Structure Bonding

FRS-186 The mounting surfaces of the FRS-E and FRS-O shall be electrically conductive to support the bonding of the units to a conductive structure.

Note: Electrical bonding through the mounting surface or fasteners is preferred over individual ground straps.

3.4.7.16 Grounding and Shielding Practices

FRS-178 The FRS-E shall implement the following grounding and shielding scheme for all

LVDS where the inner shields connect to the outer shields and the metallic connector backshell at both ends of the cable.

3.4.8 Wire Requirements

3.4.8.1 Wire Specifications

FRS-193 High strength copper wire shall be utilized or wire size #26 AWG and smaller.

3.4.8.2 MIL-DTL-27500 Wire

FRS-194 MIL-DTL-27500 twisted/twisted shielded wire shall be utilized as appropriate.

3.4.8.3 Wire Magnetic Materials

FRS-196 When used, silver plated copper wire, wire braid and shielding material shall be utilized for magnetics reasons.

3.4.8.4 Nickel Platting Specification

FRS-197 All Nickel utilized shall have high phosphorus content/low magnetic nickel platting.

3.4.8.5 Connector and Backshell Magnetics Review

FRS-198 All connectors and backshells shall be reviewed and approved by LISA Magnetics control board.

Note: The Parts Control Board (PCB) oversees the review of all LISA components. Harness containing magnetic materials including Nickel platting and/or stainless-steel hardware must be degaussed and characterized before deliver to ESA.

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3.4.8.6 Connector and Backshell Approval

FRS-199 All connectors and backshells shall be reviewed and approved by LISA Materials.

3.4.8.7 Wire Stress Relief

FRS-203 Wired electrical connections shall contain stress relief.

Note: NASA / LISA standard requires 360 deg close-out backshell which provides strain relief.

3.4.8.8 EEE-INST-002 Wire Compliance

FRS-204 All selected wire types shall meet the Wire and Cable Requirements in section W1 of

EEE-INST-002.

3.4.8.9 EEE-INST-002 Connector Compliance

FRS-205 All selected connector types shall meet the Connector and Contact Requirements defined Section C2 of EEE-INST-002.

3.4.8.10 EEE-INST-002 Current Carrying Capacity Compliance

FRS-206 The current carrying capacity of the wires and contacts shall be derated for continuous operation at the required current levels in a vacuum, as defined in EEE-

INST-002.

3.4.8.11 Harness Connector and Back-shell Grounding

FRS-209 Component connectors and back-shells of components shall be grounded. The DC resistance between connectors and back-shells should be less than or equal to 100 milliohms.

3.4.8.12 Positive and Return Wire Matching

FRS-210 The number of positive and return wires shall be equal.

3.4.8.13 Return Wire Requirement

FRS-211 Any wire that carries current greater than 100 microamps should have an associated return wire.

3.4.8.14 Plus Wire and Return Twisting

FRS-212 The plus wire should be twisted with the return wire.

3.4.8.15 Power Line and Return Twisting

FRS-213 Power lines shall be such that each line is twisted with its return.

3.4.9 Cable Shielding

3.4.9.1 Current Carrying in Cable Shields

FRS-216 Cable shields shall not be used as intentional current-carrying conductors, except in coaxial cables for RF links and high-speed data links.

3.4.9.2 Connector Conductive Finish

FRS-217 Connectors used to carry shielded wires shall have a conductive finish.

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3.4.9.3 Cable Shield Bonding

FRS-218 Cable shields shall be bonded to chassis ground at both ends, through the equipment connector body:

- using a backshell or a dedicated intermediate metal part,

- with a DC resistance ≤ 5 mΩ between cable shield and connector housing.

3.4.9.4 Overshield Bonding

FRS-219 Overshields shall be bonded to chassis ground:

- at both ends,

- using a 360° connection,

- with a DC resistance ≤ 5 mΩ between overshield and connector housing.

3.4.9.5 Shielded and Unshielded Cable Connector Separation

FRS-220 Shielded and unshielded cables shall not be combined in one connector.

3.4.10 Electrical Connectors

3.4.10.1 Agency Approval of Connectors

FRS-221 FRS connector types and locations shall be approved by NASA.

3.4.10.2 Connector Metallic Back-shells

FRS-222 Connectors shall have metallic back-shells.

3.4.10.3 Harness Bundle First Fixation Point Distance

FRS-224 The first fixation point of harness bundles to the structure shall be within 150 mm of the connector interface. If the connector’s distance from the structural mounting interface prevents this, the responsible unit or bracket shall provide means to allow fixation the affected harness bundles to the unit or bracket structure.

3.4.10.4 Connector Locking Provision

FRS-225 All Connectors shall have a locking provision.

3.4.10.5 Cable Classification Separation

FRS-227 Signals falling into different classes shall be assembled to separate connectors and cable bundles.

3.4.10.6 Cable Bundle Class Separation Distance

FRS-228 Cable bundles of different classes shall be separated either by a separation distance of

5 cm from the outer circumference or by a metallic screen when they are routed on parallel paths.

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3.4.10.7 Enclosed Contacts for Source Power and Test Connectors

FRS-229 A connector carrying source power or external test connectors on units shall utilize enclosed contacts to reduce the risk of arcing and short circuit during handling, mating and de-mating process.

Note: This can be achieved by using female D-SUB connectors with socket contacts or male

Micro-D connectors with pin contacts.

3.4.10.8 Test Connector Capping

FRS-230 Test connectors shall be capped with flight-approved RF and static control covers when not in use, including on orbit.

3.4.10.9 Connector Saver Provision

FRS-231 For test purpose, flight connectors shall be protected against multiple mating/demating operations by connector savers. Connector savers shall be compatible with flight hardware.

3.4.10.10 Connector Saver Performance Impacts

FRS-232 The use of connector savers for ground testing shall not alter the performance of the

Equipment.

3.4.10.11 Connector Keying

FRS-233 Erroneous mating shall be avoided through the use of connector keying or marking.

3.4.10.12 Connector Space Contacts

FRS-234 Except when pin allocation is imposed by a standard specification, spare contacts shall be available on each connector.

3.4.10.13 Connector Labeling

FRS-236 Each module or subsystem harness connector shall be labeled and clearly visible to facilitate proper mating.

3.4.10.14 Adjacent Connector Size and Gender Restrictions

FRS-237 Physically adjacent connectors shall be of different sizes or of different genders.

3.4.11 Test Points

3.4.11.1 Diagnostic Port Capping

FRS-308 The diagnostic port shall be appropriately terminated/capped for flight.

3.4.11.2 Test Connector Capping

FRS-309 All FRS test connectors shall be capped with a conductive cover for flight.

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3.4.12 General Data Management

3.4.12.1 FPGA Resource Utilization Review

FRS-246 Resource utilization of FPGA designs shall be reviewed and assessed in accordance with NASA procedures at each design review, with results shared with ESA.

3.4.12.2 Programmable Device Reprogramming Access

FRS-247 The FRS-E shall support reprogramming of all programmable devices without disassembly at any level of integration.

3.4.12.3 JTAG Connector Close-out Provision

FRS-249 The FRS-E JTAG connectors shall have a provision for appropriate close out/capping after final use.

3.4.13 Electrical Ground Support Equipment (EGSE)

3.4.13.1 EGSE Single Fault Tolerance to Flight Unit

FRS-251 The EGSE shall be one fault tolerant to damage the flight unit.

3.4.13.2 EGSE Flight Approved Connector Compatibility

FRS-252 EGSE cable connectors that mate with flight test connectors shall be flight-approved connectors. Military connectors such as M24308 specified connectors are acceptable;

material compatibility with TVAC must be considered.

3.4.13.3 EGSE Single Failure Propagation Protection

FRS-283 All interfaces of the EGSE to flight equipment (including the spacecraft) shall be designed such that a single failure cannot propagate to flight equipment.

Note: It is expected that the design of the EGSE incorporates protections limiting the fault voltage emission to a level acceptable by the unit.

3.4.14 Timing and Clock Requirements

3.4.14.1 Tuning Interface

FRS-14 The FRS shall implement the digital tuning interface as specified in LISA-ELEC-ICD-

0013. This interface implements the fast and slow tuning for the MO PZT and MO crystal TEC respectively.

Rationale: PZT fast and thermal slow tuning is required to meet the requirements of the laser.

3.4.14.2 FRS-E Communication and Tuning

FRS-76 The FRS-E shall activate a single communication and tuning interface with the LH

LEM upon command.

Note: Operational concept is defined in the FRS-E EICD.

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3.4.14.3 FRS-E-CTU Timing Interface

FRS-83 The FRS-E shall implement a nominal and redundant timing interface from the CTU to receive the Master Clock signals as shown in FRS-E ICD LISALSR-FRS-ICD-

0031.

3.4.14.4 FRS-E Clock Synchronization

FRS-84 The FRS-E shall provide the synchronization clock to the LFPDC with the frequency

364.7 kHz ± 5 kHz.

Rationale: The digital (clock) signal has to be synched to the spacecraft reference clock.

3.4.14.5 FRS-E Master Clock Redundancy

FRS-85 The FCC on power-up or reset shall initialize using its internal clock.

3.4.14.6 Nominal/Redundant External Clock Source Transition Command

FRS-256 The FRS shall accept an external command to transition to either the Nominal or

Redundant externally provided clock.

Note: A reset can occur at the transition of clock source. It's understood that science will not be maintained upon loss of signal.

3.4.14.7 FRS-E Master Clock Redundancy

FRS-86 The primary and redundant clock signals shall be implemented using two separate ICs to avoid failure propagation.

Rationale: The digital (clock) signal has to be synched to the spacecraft reference clock.

3.4.14.8 FRS-E Internal Clock

FRS-87 The FRS-E shall use an internal clock and operate nominally at power-up without relying on any externally provided clock.

Rationale: The digital (clock) signal has to be synched to the spacecraft reference clock.

The LS, FRS should be able to receive telecommands prior to the SC Master Clock selection.

3.4.14.9 FRS-E Internal Clock Loss Mode Transition

FRS-88 If the spacecraft clock is lost, the FRS-E shall transition to standby mode and provide critical housekeeping telemetry defined in the FRS-E EICD to the LEM.

Rationale: The digital (clock) signal has to be synched to the spacecraft reference clock.

3.4.14.10 FRS-E Clock

FRS-89 The FRS-E shall meet the functional and performance requirements when operating on the internal clock or external spacecraft clock.

Rationale: The digital (clock) signal has to be synched to the spacecraft reference clock.

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3.4.15 Survivability

3.4.15.1 FRS Survival

FRS-257 The FRS-E and FRS-O shall not suffer permanent degradation as a result of any commanding error, including operator error.

3.4.15.2 Resilience to Unannounced Removal of Power

FRS-258 The FRS-E shall be designed to survive unannounced power removal without physical damage to any internal component or interface.

3.4.15.3 Nominal-to-redundant Fault Propagation Prevention

FRS-259 The FRS-E and FRS-O shall be designed to prevent fault propagation from a nominal unit to its redundant unit or any interfaced subsystem.

3.4.15.4 FRS-E Ground-commanded Reset Capability

FRS-260 The FRS-E shall implement a ground-commanded reset capability.

3.4.15.4.1 Unpowered FRS-E Interface Survival

FRS-96 All interfaces to the FRS-E shall survive without damage or permanent degradation the interfaces being active when the FRS-E is unpowered. All interfaces to the FRS-E from the LS or SC must be cold spare and capable of surviving without damage and degradation from applied voltages of 3.9 V.

3.4.15.4.2 FDIR

FRS-254 FRS-E shall enable detection and diagnosis of any failure identified in the failure analysis (e.g., FMECA), at least down to the function or equipment level.

3.4.16 Power Interfaces

3.4.16.1 FRS-E PCB Secondary Power Return Planes

FRS-103 PCB secondary power return planes shall be connected to the FRS-E chassis, taking into consideration the generation of magnetic fields due to current loops.

3.4.16.2 Power-up

FRS-105 The FRS-E shall enter a deterministic and reproducible standby state upon power-up or reset.

3.4.16.3 FRS-E Safe State on Internal Fault Detection

FRS-262 The FRS-E shall enter a safe state upon detection of any internal fault.

3.4.16.4 Autonomous Power-on

FRS-106 The FRS shall implement autonomous power-on at the reception of the input power.

3.4.16.5 Primary Power Voltage

FRS-107 The FRS-E shall operate nominally and meet all performance requirements with an input bus voltage between 26V to 32V.

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3.4.16.6 Voltage

FRS-109 The FRS-E shall survive without damage an input voltage from 0 to 40V.

3.4.16.7 Power Supply

FRS-111 The FRS shall have a power interface connected to one LCL class 2.

Note: The consumption of the cavity (FRS-O) is the…